Are Push-on Joints OK for Force Mains?

[gt5879c]

Is PVC DR 17 with push-on joints OK for a STEP force main system with pressures up to 180 PSI. I know the pipe is OK, but are the joints able to withstand pressures that high?

 

[bimr]

You need to down rate the PVC pressure rating for long term response. You also have to restrain the joints at every change of direction.

 

[gt5879c]

I'm not sure I understand what you mean by this:

"You need to down rate the PVC pressure rating for long term response."

Can you please elaborate? Thanks.

 

[bimr]

The reliability of the design is firmly based on an assessment of the long-term strength of the PVC compound
formulation.

http://www.uni-bell.org/pubs/Chapter 5.pdf

http://www.uni-bell.org/pubs/pvc_cyclic.pdf

 

[rconner]

I didn’t happen to see the behavior you describe detailed in the treatise for the reported now most common design for such accessible at

http://www.hultec.co.za/downloads/RIEBER_SEALING_n_America.pdf.

However, I did see the claim on page 4 that “different sealing mechanisms” can be at work between pressurized and non-pressurized conditions, and a hint also that maybe some problems have in somewhat cryptic fashion been blamed on incorrect insertion with the verbiage, “Insertion of the spigot beyond the insertion mark may cause the spigot to wedge itself into the neck of the bell, thus preventing hydrostatic pressure from reaching the gasket through the gap between the pipe bell and spigot, and preventing proper functioning of the gasket…”

 

[rconner]

Oops, I meant the above response for the current inquiry on the Civil/"Water Distribution..." forum that reported small, apparently sort of temporary leakage at the beginning of a test in a new pvc pipeline (I will re-post it on the correct thread, so it could be deleted here if nec'y)